...

Width 

This specifies how wide your form will be. The default “regular” width is 600px, but the dropdown also includes thin (400px) and wide (800px). You also may pick the custom option; this will enable the box to the right of the Width dropdown and let you specify your own width.

...

You can choose a theme to alter the appearance of your form. frevvo Live Forms provides two global themes : Clear or Professional Blue. The Clear theme gives your form a clear (white) background and the Professional Blue gives your form a soft blue background.

...